Acid-resistant alloy



, 1,539,260 UNITED STATES PATENT orr'lca.

B. JACOBS, 01' WILKINGTON, DELAWARE, ASSIGNOATO E. I. DU FONT DE .mouns & COMPANY, 01' WILMINGTON, DELAWARE, A CQRPORATION F DELA- ACID-RIESI8TANT ALLOY.

WARE

Io Application Illay 8,

Toall whomi'tmayconaem: I i I.

Be a known that I, 01mm is. Jaooss,

a citizen of the United States, and a resident of Wilmington, in the county of New I Castle and Stateof Delaware, have invented a certain new and useful Acid-Resistant Alloy, of which the following is a specification. y

This invention relates to an alloy com- 10 posed'mainly of copper and silicon, and containing a sufficient amount of a third element, as for exam le manganese, to render the alloy machina 1e and workable.

The chief object of my invention is to provide an allo that is extremely resistant to the chemica action of mineral and oranic acids and other corrosive liquids, and

at at the same time possesses those physical roperties, such as high tensile strength and uctility, which will permit ofits practical use in the manufacture of reaction-vessels and various other articles or parts of chemical apparatus which are destined to be subjected to the action of corrosive chemical reagents.

I have discovered that by combinin copr with silicon, an allo is obtained havmg an exceptionally hig resistance to the action of liquids which are ordinarily regarded as corrosive. I found that silicon would combine with copper in varying prortions and that there appeared to be efinite com ounds corresponding to the formula Cu i and Cu Si with a eutectic containing 18% silicon melting at 810 C. Silicon-copper alloys of the above composition, although very acid-resistant, were found, however, to be extremely brittle. Even 5% of silicon combined with copper 40 was found too brittle and weak in structure tomeet the uses to which it was intended to at the alloy. I then discovered that the a dition of small amounts of inanganese tou hened and strengthened these alloys so t at {the productspossessed the requisite strength and other physical properties for my purpose without injury to their. corrosion-resistant pro erties.

The alloys made in accor ance with my invention may be described as having a base of copper to which ap reciable amounts of manganese and silicon ave been added for the specific purposes above noted, the silicon predominating over the manganese. The

192:. Serial in. 559,008.

alloy containsno other elements except incidental mpurities, principally iron introduced with the manganese or silicon. Using the technically pure manganese and silicon roducts now obtainable on the market the lghest iron content I have yet found in the new alloy is less than 0.2%. Of the new alloys those containing from 3 to 6.5% s1licon wit from .5 to 7% manganese, the balance being copper except for incidental 1m urities such as traces of iron in the silicon and manganese, were found to be characterized by the physical properties of first-class bronzes and when properly cast showed a tensile strength varying from 34,- 000 to 42,000 lbs. per square inch with from 10 to 37% elongation and from. 18 to 45% reduction of area depending on the manner in which they were cast and somewhat on the relative proportions of silicon and manganese in the alloy. Alloys within these limits are sufliciently ductile to permit their being worked under the proper conditions into sheets, wire and tubing or they may be used in the form of castings made either in green sand or in permanent molds.

Allo s containing from 7 to 15% of silicon with rom .8 to 3% manganese are characterized physically by greater hardness and a tensile strength upwards of 48,000 to 50,- 000 lbs. per square inch with 7 to 12% elongation and from 6 to 12% reduction in area but have hardly sufiicient ductility to work well into thin sheets or wire. It, however, would not be proper to state that alloys containing the above higher percentages of silicon can not eventually be worked as well as those containing the lower percentages. 1

These alloys may be produced by melting agiven weight ofv copper and adding toit pure manganese and pure refined silicon in the desired proportions. It is advisable as in the melting of all bronzes and similar copperalleys to first melt the copper in plumbago crucibles under charcoal to protect it against oxidation and contamination from furnace gases.- The best pouring temperature from producing sound castings is in the neighborhood of 1900-2000 F.

The preferred method and the one which gives uniformly the best results is to first produce in the electric url ace or other-..

wise, an alloy of manganese and silicon conor pure manganeseasf the case may demand to the mixture-of metals first melted. A more homogeneous alloy is produced-in a shorter time bythi's fmetho'daof procedure than when the metals 'ar all added sep- The above combination of copper, silicon and manganese 'may'be regardedas a type of bronze and be designated as a siliconmanganese bronze aiid the best results are usually obtained 'by handling the melting and pouring' of"' the"copper-' a's one would handle; ordinaiy 'bron'ze" of say '90 to 95% op'pe'r" and Tt'o tin. The addition of the same deoxidizing agents such 'as'phosphor-copp'er, boron-copper, or any of the well knowndeoxidizers used in the melting and castingof bron'zes may begused in amounts varying from 0.5 'to-2% with the same beneficial effects on'bronzes' composed of silicon, manganese, and copper so far as ph 'sical chacteristics are concerned as on or inary bronze, and used in such small quantities they "have no deleterious eflect dn'the acid-resistingproperties of the'alloy.

These 'alloys are characterized chemically by extreme resistance to various mineral and organic acids and ,other corroding uids' As an example of the resistance of oys of the above composition to corrosion With the" allovlsubmerged in concentrated liydrochloric acid (35-36% HCl), the penetration'permonth varies from 0.0012 to 0.0025"', the latter figure being obtained when the solution is agitated at the rate of 200 R. P. M. In 3 to 25% sulfuric acid the corrosion'varies from practically a passive or inertstate to 0.0006 penetration per month, the latter figure when the. solution is agitated at the rate of 200 R. P. M. The alloys are extremely resistant to dilute hydrochloric acid in the presence of oxidizing agents-as, for example, a 2 to 3% hydrochloric acid in the presence of sodium chlorate,-sh0wing practically no loss or gain in weight after exposure for sixteen days to the above solutions at a temperature of 90 C. under conditions of agitation.

There is also little or no action in the presence of ammonium chloride, zinc chloride, free. ammonia vapor and hydrogen chloride at temperatures up to 230 C. as instanced by a loss of but 0.03% in weight when subjected to a solution containing the above substances for a period of sixty hours. Steel and cast iron under the same conditions lost respectively and 22% in weight in sixty hours. v

In alum solutions up to 30 B. at the boiling point, which by hydrolysis liberates free sulfuric acid, the corrosion expressed in inches penetration per month amounted to.0.0006". At higher concentrations of alum solutions as for example 50 B. at the boiling pointthe alloys are .inert, .i.ie.,' no loss or gain'inweight.

In lactic acid, both the dark and variety of 22% strength, the alloys are inert in both -solutions at the boiling point.

Although specific referencehas been made above to copper base alloys containing from 3 to 15% of silicon, and from 0.5; to 3% of manganese, it-is to be understood that my invention-is not limited to alloys in which the constituents fallwithin these ranges of "proportions. In general there should be a suiiicient' proportion of silicon to render the alloy more resistant to acids and other corroding a ents than are copper, brass, and ordinary ronzes, and a suflicient manganese content to render the alloy machinable .and workable. The new alloys may be further defined as copper-silicon-manganese alloys in which the-copper predominates, and in silicon, and from about 0.5 to 3.0% of man ganese, said alloy bein'g machinable and workable and strongly resistant to acids.

3. An alloy comprising from about 92.5 to 96.5% of copper, from about 3 to 6.5%

of silicon, and from about 0.5 to 0.8% ofmanganese, said alloy being machinable and workable and strongly resistant to acids.

4. An acid-resistant alloy comprising from about 3 to 6.5% of silicon, most of the remainder being copper with suflicient manganese to render the alloy machinable and workable.

5. An alloy comprising from about 3 to 6.5% of silicon,'and from about 0.5 to 0.8 manganese, substantially all of the remainder being copper, said alloy having a tensile strength of from 34000 to 42000 pounds per square inch, with from 10 to 37% elongation, and from 18 to 45% reduction of area.

In testimony whereof I afiix my signature.

CHARLES B. JACOBS.

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